Recovering antimony trichloride from hydrocarbon extract phase



J. F. DETERS July 29, 1952 RECOVERING ANTIMONY TRICHLORIDE FROM HYDROCARBON EXTRACT PHASE '2 SHEETS-SHEET 1 Filed Nov. 26, 1949 INVENTOR.

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RECOVERING ANTIMONY TRICHLORIDE FROM HYDROCARBON EXTRACT PHASE Fi-led NOV- 26, 1949 2 SHEETS-SHEET 2 o v 20 4o so '80 WEIGHT RAT/0 0F BE/VZENE To .SbCL; x I00 WEIGHT RECOVERY OF SbCl IN EXTRACT PHASE 3 IN V EN TOR.

ZZZ/ 9'. Z Ja/m F Defem MMJMW l/v/Q a ATTORNEY i atenteci juiy 29, 1952 RECOVERING ANTIMONY TRICHLORIDE FROM HY DROCARBON EXTRACT PHASE John F. Deters, Valparaiso, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application November 26, 1949, Serial No. 129,558

4 Claims. (01.196-13) This invention relates to the extraction of hydrocarbon oils such as petroleum napthas, gasoline, kerosene, gas oil, cycle gas oil from cracking operations, etc., and more particularly it relates to a process of extracting such oils with antimony trichloride solvent. It is well known to extract petroleum oils with antimony trichloride, such a process being described in U. S. Patent 2,322,083, June 15, 1943. One of the problems in the use of this solvent commercially is the recovery of the solvent from the raifinate and the extract for recycle in the process.

.It is an object of this invention to improve the recovery of antimony trichloride solvent from the extract, thereby reducing the cost of this operation. It is another object of the invention to reduce the amount of water required for antimony trichloride recovery. A still further object of the invention is to reduce the amount of acid-resistant equipment required for antimony trichloride recovery.

The invention is illustrated by drawings which show in Figure 1 an apparatus suitable for carrying out the process; and in Figure 2 a graph of data typical of one phase of the process.

I have discovered that addition of benzene to the extract obtained from antimony trichloride extraction of mineral oils results in the separation of antimony trichloride as a solid phase at ordinary temperature, e. g. about 25 C. I have also found that the amount of benzene required to effect a maximum separation of antimony trichloride is about to 45 per cent of the Weight of the SbCls in the extract phase, preferably about 20 to 35 per cent. amount, I have found it possible to separate as much as 70 per cent of the SbCls from the extract as a crystalline solid which can be melted and recycled to the process without further treatment, thereby reducing the amount of SbCl3 remaining to be recovered from the extract to only one-third the amount previously required to be recovered. Some increase in SbCls separation can be obtained by operating at lower temperatures, e. g. (l to C., but this operation requires refrigeration and is not necessary for good results.

There are various ways of applying benzene crystallization to the antimony trichloride extrac- By adding benzene in this,

2 tion process.

Referring to the drawing, a suitable, charging stock, for example, kerosene, gas oil or cracking still cycle oil, is introduced by line Ill to the heater II and thence into extraction tower I2.

SbCh is introduced at an elevated point in the tower by line I3. It is desirable to maintain the.v

temperature of the tower above the point at which SbC13.Wi11 solidify. A temperature of 35 to C. is commonly suflicient for, altho the melting point of pure SbCl: is 73.4" 0., the stream thru line I3 is usually not pure and the solvent quick! I 1y absorbs constituents from the oil in tower I2 which lower its melting point;

Because of the high density of the SbCh solvent, it cascades rapidly down thru the extraction tower over suitable baffles or other contacting material and collects in the bottom, of the tower from. which it is withdrawn by line l4 leading to mixer, I5 and receivers I6. The oil passes up thru tower.

I2 and is withdrawn by line I1 leading to raffinate Washer I8 where any dissolved or entrained SbCla is removed by a stream of dilute I-ICl introducedat I9 and withdrawn by line 20 leading to SbCls recovery still 2I. drawn from the process by line 22.:

The ratio of SbClz solvent to oil treated is usual- 1y about 50 to 200per cent by weight and; the,"

major part of the SbCh forms an extract phase with aromatic constituents of the oil treated. It

has heretofore been the practice to wash the extract phase with dilute I-ICl to recover the SbCla in aqueous solution. Distillation of the hydrocarbons from the extract is not feasible because of undesirable polymerization reactions which take place at the temperature of distillation and because of the relatively high volatility of SbClg.

According to my process, I introduce benzene in the proportion of about 10 to 45 weight per cent based on SbC13 in the extract in mixer I5, line 23 being used to conduct the benzene from supply 24. The benzene-extract solution then passes by line 25 thru cooler 26 and into one of the receivers I6 where it may be further cooled by coils IBa while the SbCls precipitates as a crystalline mass, apparently in the form of a benzene complex. At 25 C. I may separate in settler I6 as much as per cent of the SbCla in the ex tract phase.

The drawing, Figure 1, shows one method by which the process may be carried out.

The washed raffinate is with- After settling of the SbCh, the extract layer is withdrawn by manifolds 21 and line 28 leading to extract washer 29 where the extract is contacted with a stream of dilute HCl introduced by line 30 and the recovered SbCh in aqueous solution is conducted by line 3| to still 2| for removal of water. Steam and hydrochloric acid are conducted by vapor line 33 to condenser 34 and thence to receiver 35 from which the dilute I-ICl may be recycled in the process by lines 32 and 36. The anhydrous liquid SbCl3 obtained in still 2| is conducted by line 31 to SbCls supply tank 38 from which it may be Withdrawn by line [3 and recycled in the process.

Washed extract from washer 29 is conducted by line 39 to stripper 40 where benzene is stripped off thru vapor line 4|, condensed in coil 42 running into receiver 43, whence the recovered benzene passes by line 44 to benzene supply 24. The

washed and stripped extract is withdrawn fromthe process by line 45.

Crystalline SbC13 in receiver l6 is melted by steam coils 46 and withdrawn by line 41 to still 48 where occluded benzene can be driven ofi to vapor line 49 leading to condenser 50 and thence to benzene supply 24. It is not always necessary to'recover the benzene from the separated SbCb, particularly if efiicient means of separating'the solidified solvent are employed such asfiltration or-centrifugal separation. In that case, still 48 may be suitably bypassed by broken line as shown in the drawing. Recovered SbCls is conducted by line 52 to'supply tank 38 for further use in-the process.

As an example of the application of my process to an aromatic-containing petroleum stock for recovery of aromatics, a light catalytically cracked cycle stock obtained from the fluid catalyst cracking process was extracted with 30 volume per cent (108 weight per cent) of SbC13 at*25' C. The rafiinate phase contained 54.8 per cent by weight of the oil and 11.7 per cent by weight of the SbCls. The remainder of the SbCls was found in the extract phasepi. e. 88.3 Weight per cent of the total or 68 per cent of-the weight -of the'extract. The addition-of 18per' The sulfur analysis was: Extract2.05%; rafmate-0.32%.

Figure 2 of the drawing shows the amount of SbClz expressed in percentage which is caused to c'ry's'tallize by the addition of varying amounts of'benzene to the extract from the light catalytic cycle oil iustdescribed. The temperature of separ a-hon was-25 C. I y

Anbtherextraction at 25 C. of light cycle oil Suli from catalytic cracking using 20 per cent by volume of SbCls based on the oil treated gave an extract yield of 39 per cent by volume. The properties of the feed, extract and rafiinate fractions obtained are given below:

Refractive Index N3 llr 2. O4

Having thus described invention, what I claim is:

1. In a process wherein a hydrocarbon oil is extracted with antimony trichloride under conditions to form a raffinate phase containing only a minor amount of antimony trichloride and an extract phase containing most of the antimony trichloride,-the method of removing the antimony trichloride from the extract phase which comprises adding to the extract at a temperature in the range of 0 C. to 25 C. about 10 to 45 per cent of benzene, based on the weight of antimony trichloride in said extract, thereby causing the crystallization of a solid antimony trichloride material, separating said solid antimony trichloride material from the remaining liquid extract and separately removing the remaining antimony trichloride from the remaining extract.

2. The method of claim 1 which includes the 3. The method of claim- 1 which includes the) steps of stripping benzene from separated solid antimony trichloride'material to separate benzene from antimony trichloride, recycling'antimony trichloride in liquid form to the extraction step and recycling benzene for contacting further extract material.

4. The method of claim 1 which includes the steps of cooling the mixture of added benzeneand extract to increase the amount of antimony trichloride material solidified, separating the solidified antimony trichloride material from liquid extract material, distilling benzene fromantimony trichloride'material to: obtain benzene and molten antimony trichloride, recycling :the'

molten antimony trichloride to the extraction step and recycling the benzene forcontact with further-extract.

REFERENCES CITED The following references are of "record in "the file of this patent:

UNITED STATES PATENTS Number Name Date 2,246,257 Kohn June 17, 1941 2,322,083 Plas June 15, 1943" JOHN T F. DE-IERSJ V I 

1. IN A PROCESS WHERENIN A HYDROCARBON OIL IS EXTRACTED WITH ANTIMONY TRICHLORIDE UNDER CONDITIONS TO FORM A RAFFINATE PHASE CONTAINING ONLY A MINOR AMOUNT OF ANTIMONY TRICHLORIDE AND AN EXTRACT PHASE CONTAINING MOST OF THE ANTIMONY TRICHLORIDE, THE METHOD OF REMOVING THE ANTIMONY TRICHLORIDE FROM THE EXTRACT PHASE WHICH COMPRISES ADDING TO THE EXTRACT AT A TEMPERATURE IN THE RANGE OF 0* C TO 25* C. ABOUT 10 TO 45 PER CENT OF BENZENE, BASED ON THE WEIGHT OF ANTIMONY TRICHLORIDE IN SAID EXTRACT, THEREBY CAUSING THE CRYSTALLIZATION OF A SOLID ANTIMONY TRICHLORIDE MATERIAL, SEPARATING SAID SOLID ANTIMONY TRICHLORIDE MATERIAL FROM THE REMAINING LIQUID EXTRACT AND SEPARATELY REMOVING THE REMAINING ANTIMONY TRICHLORIDE FROM THE REMAINING EXTRACT. 